1. Field of the Invention
The invention relates in general to snowmobiles and, more particularly, to a snowmobile with a movable rear snow flap.
2. Background of the Invention
In general, a snowmobile has a central frame or chassis on or around which the various components of the snowmobile are assembled. Typically, a pair of skis are mounted at the front portion of the chassis and an internal combustion engine drives a ground-engaging track that is centrally mounted under the chassis.
In conventional snowmobiles, the track is provided under the chassis in such a manner that the entire length of the track is located beneath the xe2x80x9ctunnelxe2x80x9d formed by the chassis, as illustrated in FIG. 1. A snow guard typically is provided at the rear of the chassis to prevent snow that the track engages from spraying excessively in an upward or rearward direction.
In contrast, in the snowmobile disclosed in U.S. patent application Ser. No. 60/167,614, the length of the chassis is reduced and a rear portion of the track extends beyond the rear end of the chassis. As discussed in that provisional patent application, such a configuration improves the maneuverability and overall performance of the sled. In particular, shortening the chassis reduces the overall weight of the snowmobile and, hence, reduces the polar moment of inertia, thereby allowing the snowmobile to turn more quickly. Shortening the chassis, however, exposes part of the rear portion of the track and leaves that rear portion uncovered, which may result in greater amounts of snow being splashed or sprayed upwardly and/or rearwardly than is desired.
Furthermore, when the entirety of the track system is positioned under the chassis, as in conventional snowmobiles, the chassis limits the range of xe2x80x9ctravelxe2x80x9d of the rear suspension system. In particular, it has been observed that as a conventional snowmobile moves over uneven terrain, as the track system moves to the upper limit of the range of travel or the rear suspension system, the rotating track may strike the undersurface of the chassis.
It is generally believed that a rear suspension system with a greater range of movement performs better than a rear suspension system with a more limited range of movement. Previously, attempts to increase the range of movement of the rear suspension system have been made either by changing the tilt angle of the chassis or by rearranging the components of the rear suspension system.
Accordingly, it is an object of the invention to overcome these limitations or drawbacks of snowmobiles according to the prior art.
In one aspect, the invention features a snowmobile in which the chassis is shorter than in conventional snowmobiles and does not extend over the entire track. Rather, the track extends longitudinally rearwardly beyond the rear end of the chassis. This reduces the weight of the snowmobile and hence, because the length of the chassis is reduced, the polar moment of inertia of the snowmobile. This reduction in weight and polar moment of inertia improves maneuverability and overall performance of the snowmobile.
Because the end of the chassis does not shield the track system from spraying snow up and/or rearwardly, a pivotal snow flap is provided above and extending beyond the rear portion of the track to prevent or substantially reduce the amount of snow sprayed by the tread as the snowmobile moves through the snow. The snow flap is pivotally connected at its forward end to the rear end of the chassis and is caused to pivot by virtue of its connection to the track system by means of linkage struts. The linkage struts are pivotally connected to a portion of the snow flap and to the track system. This arrangement causes the snow flap to pivot relative to the chassis as the track system moves through its range of travel and keeps the track shielded. Additionally, because the snow flap moves with the rear suspension travel, the tread will not contact the snow flap and/or the chassis, and hence will not abrade and degrade those components.
In another aspect, the invention features a handle-shaped bumper that is connected to the snow flap. Because the snow flap is connected to the track system, it is easier to lift the rear of the snowmobile when necessary to do so, e.g., when lifting the snowmobile out of a small gully. This is because the lifting action acts virtually directly on the track system via the bumper (which is connected to it), whereas in the prior art, it was customary to lift through a bumper mounted at the rear of the chassis and a certain degree of lifting motion was lost as the chassis rose relative to the track system (as the xe2x80x9cplayxe2x80x9d in the suspension system was being taken up) before the tread ever began to be lifted from the ground. Additionally, lifting the rear end of the snowmobile according to the invention is easier with the bumper connected to the snow flap than the case where the bumper extends from the rear of the chassis because the lower position requires a person lifting the rear of the snowmobile to bend from the knees to reach it, whereas the prior art arrangements only required the person to bend from the waist to reach the bumper, and it is easier to lift xe2x80x9cwith the legsxe2x80x9d than xe2x80x9cwith the back.xe2x80x9d